Electrolyte for lithium secondary battery and lithium secondary battery including the same

Abstract

An electrolyte for a lithium secondary battery according to exemplary embodiments may include an organic solvent, a lithium salt, and an additive including a polyalkylene glycol dialkyl ether compound having a weight average molecular weight in a specific range.

What is claimed is: 
     
         1 . An electrolyte for a lithium secondary battery comprising:
 an organic solvent;   a lithium salt; and   an additive including a polyalkylene glycol dialkyl ether compound having a weight average molecular weight (Mw) of 1,000 to 20,000.   
     
     
         2 . The electrolyte for a lithium secondary battery according to  claim 1 , wherein the number of carbon atoms of alkyl groups at both ends of the polyalkylene glycol dialkyl ether compound is each independently 1 to 4. 
     
     
         3 . The electrolyte for a lithium secondary battery according to  claim 1 , wherein the polyalkylene glycol dialkyl ether compound includes a polyethylene glycol dialkyl ether compound. 
     
     
         4 . The electrolyte for a lithium secondary battery according to  claim 1 , wherein the polyalkylene glycol dialkyl ether compound is represented by Formula 1 below: 
       
         
           
           
               
               
           
         
         (in Formula 1, R 1  and R 2  are each independently an alkyl group having 1 to 4 carbon atoms, R 3  is hydrogen or a methyl group, and n is 20 to 450). 
       
     
     
         5 . The electrolyte for a lithium secondary battery according to  claim 1 , wherein the polyalkylene glycol dialkyl ether compound has a weight average molecular weight of 2,000 to 5,000. 
     
     
         6 . The electrolyte for a lithium secondary battery according to  claim 1 , wherein the polyalkylene glycol dialkyl ether compound is included in an amount of 0.1 to 2.5% by weight based on a total weight of the electrolyte. 
     
     
         7 . The electrolyte for a lithium secondary battery according to  claim 1 , wherein the polyalkylene glycol dialkyl ether compound includes polyethylene glycol dimethyl ether. 
     
     
         8 . The electrolyte for a lithium secondary battery according to  claim 1 , wherein the organic solvent includes a linear carbonate solvent and a cyclic carbonate solvent. 
     
     
         9 . The electrolyte for a lithium secondary battery according to  claim 1 , further comprising an auxiliary additive including at least one of a fluorine-containing cyclic carbonate compound, a sultone compound, a cyclic sulfate compound, and a fluorine-containing lithium phosphate compound. 
     
     
         10 . The electrolyte for a lithium secondary battery according to  claim 9 , wherein the auxiliary additive comprises a fluorine-containing cyclic carbonate compound, an alkyl sultone compound, an alkenyl sultone compound, a cyclic sulfate compound, and a fluorine-containing lithium phosphate compound. 
     
     
         11 . The electrolyte for a lithium secondary battery according to  claim 9 , wherein the auxiliary additive is included in an amount of 1 to 5% by weight based on the total weight of the electrolyte. 
     
     
         12 . The electrolyte for a lithium secondary battery according to  claim 9 , wherein a ratio of the content of the auxiliary additive to the content of the polyalkylene glycol dialkyl ether compound is 1 to 5. 
     
     
         13 . A lithium secondary battery comprising:
 a cathode;   an anode;   a separation membrane interposed between the cathode and the anode; and   the electrolyte for a lithium secondary battery according to  claim 1 .   
     
     
         14 . The lithium secondary battery according to  claim 13 , wherein the cathode includes a cathode active material including a lithium-transition metal oxide, and
 the lithium-transition metal oxide includes 80 mol % or more of nickel based on the total number of moles of all elements except for lithium and oxygen.